In the field of control of vehicles such as automobiles, a progress has been made in recent years in development and research of control technologies to deal with a crashing of an own vehicle with preceding objects existing in front of the own vehicle. Examples of such control technologies include a control for preventing or avoiding the crashing of the own vehicle with the preceding objects, and a control for protecting occupants of the own vehicle upon crashing of the own vehicle. A typical and well-known control technology of the former type of control is a so-called “ACC” (Auto-Cruise Control, or Adaptive-Cruise Control), which is generally a control technique to adjust an output of a drive power source such as an engine device of the own vehicle, so that the own vehicle is cruising following or tracing a preceding vehicle so as to maintain a predetermined relationship such as a distance between the two vehicles. On the other hand, a typical and well-known control technology of the latter type of control is a so-called “PCS” (Pre-Crash-Safety) control, which is generally a control technique to forecast a crashing of the own vehicle and activate seatbelts and other occupant protective devices prior to the crashing. These crash-safe vehicle control technologies are desired to be more practically effective to deal with the vehicle crashing.
For example, JP-A-2000-142321 and JP-B2-2946995 disclose techniques for detecting an object existing in front of the own vehicle, determine a possibility of crashing of the own vehicle with the object on the basis of detected distance and relative speed between the own vehicle and the object, and activating pre-tensioners of seatbelts. These techniques are common crash-safe controls to deal with a crashing of the own vehicle with the preceding objects. To effect the crash-safe controls, it is desirable to accurately detect the positional relationship between the own vehicle and preceding objects which have a high possibility of crashing with the own vehicle. JP-A-2003-296350 discloses an example of a technique for accurately obtaining the positions of ambient objects surrounding the own vehicle or existing in the neighborhood of the own vehicle.
The conventional crash-safe controls are generally effected on the basis of the condition of a vehicle immediately preceding the own vehicle, as disclosed in JP-A-2000-95130. On the other hand, JP-A-5-238367 discloses a crash-safe control of the own vehicle, wherein information on a second preceding vehicle running in front of a first preceding vehicle immediately preceding the own vehicle is obtained to determine a possibility of collision between the first and second preceding vehicles, and to control the own vehicle so as to avoid its crashing.
The above-identified publication JP-A-2003-296350 disclosing the technique relating to a device arranged to detect a width and other information of each object is unclear as to how this technique is practically embodied to effect crash-safe controls of the own vehicle. The detecting device disclosed therein is operable on an assumption that each object such as a preceding vehicle running in front of the own vehicle has a wave reflecting portion or reflector, so that the width and other information of the preceding vehicle can be detected on the basis of the wave reflected from the reflector. However, automotive vehicles presently available do not have such a specific reflector. That is, the technique in question is not practically effective, and requires future establishment of an infrastructure that permits practical utilization of this technique.
The technique disclosed in the above-identified publication JP-A-5-238367 is considered an advanced crash-safe vehicle control technique in its capability of avoiding multiplex crashing of a plurality of vehicles running in succession. However, this technique requires a transmitter provided on the first preceding vehicle running immediately in front of the own vehicle, or on any ground communication facility, so that information on the second and further preceding vehicles preceding the first preceding vehicle is received from the transmitter by the own vehicle. In this respect, this technique is not practically effective, either, and requires future establishment of an infrastructure for communication between the vehicles and between the own vehicle and the ground communication facility, which permits the own vehicle to obtain running speeds of the preceding vehicles and distances between the own vehicle and the preceding vehicles.